SHA256 was recently added to the Hasher class in order to be used
in the TokenService. A few tests were still using values() to get
the available algorithms from the Enum and it could happen that
SHA256 would be picked up by these.
This change adds an extra convenience method
(Hasher#getAvailableAlgoCacheHash) and enures that only this and
Hasher#getAvailableAlgoStoredHash are used for getting the list of
available password hashing algorithms in our tests.